I. Field of the Invention
This invention relates generally to apparatus for optimizing the performance of energy consuming machines or systems and more specifically to an improved digital electronic device for demonstrating the effect of the optimization device on system performance by allowing selective control and manual intervention over the operation of the device.
II. Description of the Prior Art
Dr. Paul H. Schweitzer has made a number of inventions relating to controllers for use with internal combustion engines or other types of energy consuming systems wherein a given control parameter, such as air/fuel ratio, spark setting or other setting, is perturbated and the resulting affect on the machine or system performance is measured for producing a control signal which is then used to adjust the parameter control setting in a manner tending to improve the system's performance. In this regard, reference is made to the Schweitzer U.S. Pat. No. 3,142,967 and the Schweitzer et al U.S. Pat. Nos. 4,026,251 and 4,130,863 which are hereby incorporated by reference for their teaching of the basic servo control philosophy and various alternative implementations ranging from electromechanical to digital electronic.
The present invention is related to the subject matter of the aforereferenced Schweitzer inventions and is specifically directed to a test instrument which may be coupled to an energy consuming system for allowing manual control and intervention over various operating parameters of the system and the control mechanism itself. For purposes of illustration, the present invention will be considered in conjunction with its use with internal combustion engines, e.g., automobile engines, it being understood, however, that the optimization scheme employed is equally applicable to a wide variety of other energy consuming systems.
To demonstrate the efficacy of engine performance optimization using a dither principle, the present invention has been devised whereby it may be coupled to the ignition system of an internal combustion engine and receive, as its input, pulses from the breaker points, as well as pulses from a transducer which are proportional in number to the engine's output shaft speed. Its output is a firing pulse and the system of the present invention permits the time of occurrence of this firing pulse to be adjusted in an advance or retard direction with respect to the top dead center position, such that the system continually seeks a point corresponding to the minimum advance that gives the best torque output, hereinafter referred to as MBT.
As is pointed out in the aforereferenced Schweitzer et al '863 Patent, it is sometimes desirable for an engine to operate at other than MBT. Specifically, at MBT, some engines are found to exhibit knock or the NOX emissions may be excessive. Accordingly, it may be desirable to introduce a predetermined degree of "bias" whereby the system will be made to operate with a timing different from MBT. The apparatus of the present invention permits both a coarse and a fine adjustment over the amount of bias so that the overall effect of the bias on system performance can be studied.
In that the optimizer system concept depends upon predetermined perturbations of a engine's control parameter, e.g., spark setting, throttle position, etc., it is desirable to be able to selectively adjust both the magnitude of the perturbation as well as its frequency. In the test instrument of the preferred embodiment, the automotive engineer or technician may, through the use of manually settable switches, adjust these parameters of the dither or perturbation.
It has further been found in the analysis of certain engine types that the response curve of output torque or speed versus spark setting is fairly flat and, as a result, the MBT point is ill-defined. The optimizing concept causes small step-by-step changes in a parameter setting until further changes in the same direction result in a reduction in output performance. With very flat curves, MBT may go undetected and the repeated increments of correction could result in the timing entering a misfire zone associated with an adjacent cylinder. To obviate this problem, the device of the present invention permits both a frontstop and a backstop value to be entered into the electronics, such that correction can only occur in the range between the frontstop value and the backstop value. Again, the exact positioning of these frontstop and backstop values with respect to a reference point is selectable by the operator.
Because of the nature of the device being controlled (an internal combustion engine), inherent "noise" oscillations may cause problems relative to the establishment of a correction factor for the control parameter. As such, a means of filtering these noise oscillations may be expedient. The present invention incorporates circuitry, referred to as the digital buffer, which functions to inhibit any corrections, either positive or negative, until a predetermined number of successive correction steps in the same direction have occurred. This predetermined number is established by the manually operable digital buffer switches on the test instrument.
Another feature found to be desirable in an instrument of the type under consideration is so-called manual step correction. Switches are provided whereby the operator, by successively actuating the switches, may apply incremental corrections to the engine's control parameter. By further including a digital display panel, the operator can, through the manipulation of the manual step correction switches, track or plot the performance characteristics of the engine under control of the optimizer unit.